I.P. injection studies with sodium chromate, zinc potassium chromate, and chromium carbonyl were conducted on mice to compare the genotoxic effects of the hexavalent salts with their potential myelotoxic effects. At the doses employed, there were no significant elevations of micronucleus frequencies caused by any of the three chromate salts. Studies of the absorption and target organ toxicity of antimony potassium tartrate were completed in rats and mice given i.p. injections for 7 or 14 weeks. Dose- related levels of antimony accumulates in the liver, blood, kidney, spleen, and heart, but there were no biochemical changes indicative of toxicity except in the liver. Hepatocyte degeneration and multifocal liver degeneration occurred in association with dose-related elevations in activities of the liver-specific serum enzymes, sorbitol dehydrogenase and alanine aminotransferase. Alteration of the site of injection and the days of treatment demonstrated that the i.p. route could be practically used as a route of administration in 2-year studies. Similar studies were conducted in rats and mice administered ferrocene by inhalation for 14 or 90 days. Lung burdens of iron were increased in proportion to dose and time. The only toxic response was subacute, necrotizing inflammation of the olfactory epithelium in the nasal turbinates of both species after 14 days administration, and degeneration, inflammation, hyperplasia, and metaplasia (rats only) after 90 days administration. Studies terminated.